1. Field of the Invention
The present invention relates to an image processing technique for obtaining a synthesized image having improved image quality and graphic effect by synthesizing two images.
2. Description of the Background Art
Conventionally, there have been proposed image processing techniques wherein using two images of different image qualities that have been captured for the same subject, an image having improved image quality and graphic effect compared to the original images is synthesized.
As one example according to the conventional art, a technique for correcting a blur wherein a plurality of images that have been captured at a shutter speed which is short enough so as not to be influenced by a blur are additively synthesized in accordance with the amount of blur is known.
As another example according to the conventional art, it is known that image data wherein any subjects at different positions are in focus can be obtained by synthesizing image data that has been obtained by capturing images while changing the focus position.
Further, U.S. Pat. No. 5,162,914 publication discloses a camera having a substantially widened dynamic range by capturing odd fields and even fields while changing the exposure time and synthesizing unblurred parts of these fields.
Further, U.S. Pat. No. 5,402,171 publication discloses a technique for improving resolution of image by synthesizing an image from image data captured while moving the image pickup device.
Practically, in the case of capturing two images for the same subject with a digital camera or the like, the images are captured at different timings and a small movement of the subject or movement of the camera itself will occur in this time lag of exposure. For this reason, a small difference in position arises between these two captured images.
In the case of synthesizing the above-mentioned two images, it is necessary to carry out positioning on these two images prior to synthesizing the images while taking such a positional difference between these images into consideration. If these images are synthesized without carrying out such positioning accurately, which leads rather deterioration of image.
Furthermore, it is general that when an image is captured via a lens in a digital camera or the like, so-called “shading” that the level of image data decreases with distance from the center of the image to the periphery. However, conventionally, in the case of synthesizing the above-mentioned two images, positioning of images was carried out without taking an influence of shading into account, so that deterioration in image quality resulted due to unsatisfactory positioning between images in some scenes.